IN HIGH DUNGEON: Fetish slave Frankie Santiago (left) enjoyed her high jinks with investment banker Edward Sonderling — until he strayed.

She enjoyed the daily morning whippings — but she did not like being kicked to the curb by her beloved master.

Frankie Santiago embraced a role as live-in fetish slave to dominating Manhattan investment-banker beau Edward Sonderling, playing out a bondage fantasy similar to college student Anastasia Steele and older Christian Grey in the erotic novel “Fifty Shades of Grey.”

But it all took a twisted turn when Santiago, 27, found out Sonderling, 53, had been training his whips on her replacement.

The submissive Santiago exploded in a fit of rage, law-enforcement sources said, allegedy shattering Sonderling’s car windshield and bombarding him with dozens of text threats.

“If I ever see you with her I will not hold back. I have nothing to lose,” Santiago railed in one text. “I hope she has a disease you catch.”

Santiago — who is known in the bondage-domination S&M community as Althea Lyn — was arrested Monday after what sources said was a knock-down, drag-out fight with Sonderling at the East 57th Street apartment where she once did his daily bidding.

She was arraigned yesterday on charges of stalking, criminal mischief and aggravated harassment.

Santiago and Sonderling — who has the body of a much younger man and is known as King Eddo — were regulars on Manhattan’s BDSM circuit, where Sonderling boasted of being a “whipping aficionado,” said a source who knows the pair.

She was his live-in slave for about three years, the source said. “Basically, she was there to serve his sexual needs. She’s his toy, his fetish slave.”

At one downtown fetish event, a source recalled Sonderling openly whipping Santiago and boasting, “She has had a lot of practice. I whip her every morning before breakfast.”

Scads of photos posted on social media sites show the two — clad in leather, latex rubber and bondage gear — hamming it up and grinning for the cameras.

Sonderling chronicles his escapades, which have taken him around the world, in dozens of pictures on his MySpace page.

A Horace Mann and Brown graduate, Sonderling runs his own firm, Priority Investors LLC, He declined to comment on Santiago’s arrest and his extracurricular BDSM activities.

“I don’t think that I have anything to say about it. Why would I?” he said.

Law-enforcement sources said Santiago and Sonderling’s relationship took a twisted turn when she discovered he was seeing someone else.

Shedding her submissive role, Santiago confronted Sonderling in his apartment on July 29. At one point, she pulled a kitchen knife and threatened to kill herself, the sources said.

Sonderling managed to get Santiago out of the house and into his car, where she kicked out the front window with her foot.

Whipped into a frenzy after discovering airline tickets for Sonderling’s new partner at the apartment, Santiago called JetBlue posing as his current girlfriend and canceled the reservation, sources said.

She also allegedly opened an e-mail account in the investment banker’s name, bombarding her replacement with messages disparaging Sonderling.

From July 30 to Aug. 11, Santiago sent 40 texts to Sonderling, according to the criminal complaint.

“I hope you and [the new girl] rot in hell,” she fumed. “I hope karma gets both of you, you rotten piece of s–t.”

And, in a shot toward Sonderling’s elderly mom, Santiago raged, “I hope your mother croaks at the sight of another one of your sluts.”